Pittsburgh Steelers All-Pro linebacker James Harrison has recently revealed that he has sustained numerous undisclosed concussions in his career and as a result, is taking extra steps to protect his head.

According to a report by ESPN, Harrison — known as one of the most vicious hitters in the NFL — began using a special layer of padding inside of his helmet last season and since then hasn’t “seen any spots or had any blackouts”.

The 2009 NFL Defensive Player of the Year also said “to protect my head I’d take a pound more” and “if something works I’m going to use it”, in reference to the about three to four ounces of CRT (Concussion Reduction Technology) padding, which, according to SB Nation, is a ” sort of sandwich of military-grade kevlar and a foam which disperses energy.”

Since making the switch, Harrison has been joined by around 100 players over the last 12 months who have began using CRT padding in their helmets and uniforms.

Prior to using the military-grade kevlar in his helmet, James endured “double digit” concussions, but says he’s never missed a game as a result of the injuries.

Now he’s willing to take extra measures that he doesn’t believe the league cares to enforce.

“The league is mandating next year that we wear thigh and knee pads. I don’t know how many people’s career has been ended on a thigh or knee bruise,” said Harrison. “We have guys now that are 30, 31 years old that are having to quit the game because they have severe headaches.”

James Harrison and the Steelers (2-3) head to Ohio Sunday to take on Cincinnati Bengals.